In recent years, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. In addition, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (Plug-in HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuels.
In addition, technology related to a power storage apparatus that stores electric power and stably supplies the stored electric power to a power system when needed has been developed. The power storage apparatus is an apparatus that stores electric power when power demand is low and supplies the stored electric power in case of overload or emergency. The power storage apparatus provides the effect of improving quality of electric power and energy efficiency. In particular, a market for a household power storage apparatus and a middle-sized industrial or commercial power storage apparatus has been rapidly expanding as the power storage apparatuses are related to smart grid technology.
Meanwhile, for a battery module to provide output and capacity required by a predetermined apparatus or device, it is necessary for the battery module to be configured to have a structure in which a plurality of battery cells is electrically connected to each other in series or in parallel. In addition, it is necessary for the battery module to be configured to have a structure which is easily extendable and stable as the capacity of the battery module is increased.
Particularly, in a case in which a plurality of battery cells is used to constitute a battery module, overvoltage may be applied to some of the battery cells, overcurrent may flow in some of the battery cells, or some of the battery cells may overheat, with the result that safety and operation efficiency of the battery module may be seriously concerned. For this reason, it is necessary to provide a means for detecting such overvoltage, overcurrent, or the overheating to control the battery module. Consequently, the battery module includes a safety system, such as a battery management system (BMS), which detects such overvoltage, overcurrent, or the overheating to control and protect the battery module.
Ring terminals are connected to electrode terminals of the battery cells such that the BMS measures voltage. A process of connecting the ring terminals to electrode terminals of the battery cells is performed together with a process of connecting the battery cells in series or parallel to each other using busbars. In the processes, the ring terminals may be cut or damaged due to the rotation of the ring terminals when the busbars and the ring terminals are fastened to the electrode terminals of the battery cells using bolts since the ring terminals are not fixed but easily rotate.
Therefore, there is a high necessity for technology that is capable of fundamentally solving the above problems.